Lying on Shoulders is one of the Acro Yoga or Partner Acrobatics standing poses for beginners.Tips for a Base
Stand with your feet shoulder width apart for better stability. Move your neck and head forward a little bit so the Flyer has a space where to lay down.
Tips for a Flyer
Most important here is to not lay down too far and put too much weight on Bases arm. Your center of weight must be above Bases legs. That means your pelvis needs to be above one shoulder and your belly behind his head.